JPH01162586A - Laser beam machine - Google Patents

Abstract

PURPOSE:To constrain the lens thermal efficiency of a beam splitter and to obtain a stabilized beam diameter always even if the laser light output varies by optimally controlling the cooling of a beam splitter according to the output of the laser light. CONSTITUTION:The laser light 2 outputted from a laser oscillator 1 is split into a reflecting laser light 7 and transmitting laser light 8 by a beam splitter 6. The nozzle 9 injecting the gas for cooling is provided to the beam splitter 6 to feed the cooling gas from a cooling gas feeding device. The cooling effect is increased by increasing the flow of the cooling gas but the adhesion of a stain onto the beam splitter is simultaneously promoted and the lens thermal efficiency is furthered to the contrary by the absorbing action of the laser light 2 at the part where a stain is sticked, hence it is necessary that the flow is to be of the min flow amt. in the range capable of constraining the effect. Now the optimum flow Fopt for cooling in the set laser light output is operated by an optimum flow arithmetic device and the flow is controlled by a flow control device 12 based thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a laser processing apparatus equipped with a beam splitter, and particularly relates to means for preventing the thermal lens effect of the beam splitter.

(Prior Art) Generally, a laser processing device is configured as shown in FIG. The workpiece 5 is irradiated.

Furthermore, in a laser processing device equipped with a function to split the laser beam output, as shown in FIG. A part of the incident laser light 2 is reflected by the beam splitter 6, the laser light 8 transmitted through the beam splitter 6 is used for laser processing, and the reflected light 7 reflected by the beam splitter 6 is used for stabilizing the laser light output. Used as a monitor signal or other laser processing beam.

(Problem to be solved by the invention) Generally, the beam splitter 6 has a certain absorption rate and absorbs a part of the laser beam 2, but the absorbed laser beam is converted into heat and causes thermal distortion. Due to this thermal distortion, the beam splitter 6 has a light condensing effect, producing a so-called thermal lens effect.This thermal lens effect becomes more pronounced as the laser output increases, and the laser beam 8 transmitted through the beam splitter 6 is Focus the light,
As shown in FIG. 3, the beam diameter of the transmitted light decreases as the laser light output P increases.

The puff density W of the laser beam is given by the following formula 0 corresponding to the output P of the laser beam 2 and the diameter d of the condensed spot by the condensing lens 4.

On the other hand, the condensing spot diameter d corresponds to the condensing coefficient K of the laser beam 2 in the transverse mode, the focal length f of the condensing lens 4, the incident beam diameter D to the condensing lens 4, and the wavelength λ of the laser beam 2. It can be given by the following formula 0.

From the equation (■■), the power density W is expressed by the following equation 0.

When the laser beam passes through the beam splitter 6, a thermal lens effect occurs in the beam splitter 6.

It is necessary to consider the focal length of the combination lens.If the thermal lens effect of the beam splitter 6 is f's, and the distance between the beam splitter 6 and the condenser lens 4 is L, then the equivalent focal length of the combination lens is f's. q is expressed by the following formula (a).

If we further transform the equation (to), we get

becomes.

Also, the spot diameter d when transmitted through the beam splitter 6 from the 0 type. q is expressed by the following formula.

Generally, in laser processing equipment, L>f.

Equivalent focal length f. q is larger than the focal length f of the condenser lens 4, and feq>f (2).

The relationship deq>d (8) is obtained from the above formula Light condensing characteristics, which are important for performance, deteriorate.

Further, as mentioned above, the thermal lens effect of the beam splitter 6 increases as the laser light output P increases, and as the laser light output P increases, the diameter of the φ beam incident on the condenser lens 4 becomes smaller, and the condenser lens Since the power density applied to the condenser lens 4 increases, the thermal stress generated in the condenser lens 4 increases, the safety factor decreases, and the risk of damage increases.

Furthermore, in the case of a processing device in which the output P of the laser beam 2 is equally divided by the beam splitter 6 and the same processing is performed simultaneously in multiple processing stations, the beam diameter of the reflected light 7 by the beam splitter 6 is not affected by the thermal lens effect. Therefore, the beam diameter I) as of the transmitted light 8 is subject to the thermal lens effect.

Even if the output P of the laser beam 2 is divided into equal parts, the processing station uses the reflected light 7.

In the machining process using the transmitted light 8, the power density of the focused laser beam 2 is different, resulting in a problem that the machining characteristics are different.

The present invention was made in consideration of the above-mentioned problems, and an object of the present invention is to provide a rational laser processing device that can always obtain a stable beam diameter by suppressing the thermal lens effect of the beam splitter. There is.

[Structure of the invention]

(Means and effects for solving the problems) The present invention splits the beam light output from a laser oscillator into transmitted light and reflected light through a beam splitter, and the transmitted light is used as a processing beam,
In a laser processing device where the reflected light is used as a beam for processing or monitoring, cooling gas or cooling air is injected to the beam splitter to cool the beam splitter.

In addition to providing a cooling device to suppress the lens effect caused by the thermal distortion, the flow rate of cooling gas or cooling air is controlled to an optimal value in accordance with the output of the laser beam, and thereby the transmitted beam due to the thermal lens effect of the beam splitter is The reduction in diameter is suppressed to make the beam diameter uniform, and the beam energy is made uniform to improve processing characteristics.

(Example) An embodiment of the present invention is shown in FIG.

In FIG. 1, the configuration up to the point where a laser beam 2 outputted from a laser oscillator 1 is split by a beam splitter 6 is the same as the conventional configuration shown in FIG. 9.

In FIG. 1, the beam splitter 6 is further provided with a nozzle 9 for ejecting cooling gas (including air), and the cooling gas is supplied from a cooling gas supply device 10.

As the flow rate F of the supplied cooling gas increases, the cooling effect increases, but at the same time, the adhesion of dirt to the beam splitter 6 is promoted, and the laser beam 2 is
Since the thermal lens effect is conversely promoted by the absorption effect of

This flow rate is the optimum flow rate F OPT corresponding to each laser output.
The relationship is shown in Figure 4.

In Fig. 4, if the laser output P is P≦Ps, FOPT”OlP) If Ps, FOPT=K
It becomes t・P-.

Here P3. □ and 2 are the threshold output, proportionality constant, and constant of the thermal lens effect determined by the laser oscillator 1 that outputs the laser beam 2, respectively.

The reason why F=O in the region of P≦Ps is that when the output level of the laser beam 2 is low, almost no thermal lens effect occurs.

The optimum flow rate calculating device 11 in FIG. 1 calculates the optimum flow rate F OPT of the cooling gas at the set laser light output P based on the above relational expression, and calculates the calculated optimum flow rate F. The flow rate controller 112 controls the flow rate F so that PT is obtained.
FIG. 2 shows the calculation processing flow of the optimum flow rate calculation device 11.

In this way, by cooling the beam splitter with the optimal flow rate of cooling gas according to the output of the laser beam, it is possible to suppress the thermal lens effect and obtain a laser beam with a stable beam diameter at all times.

In the above embodiment, the set output P is input to the optimum flow rate calculation device 11, but in the case of a laser processing device that extracts the reflected light 7 from the beam splitter 6 as a monitoring detection light for stabilizing the laser light output. As shown in FIG. 5, the reflected light 7 is converted into an electric signal vF by the sensor 13, and this electric signal VF is input into the optimum flow rate calculation bag @11 to calculate the optimum flow rate F.
It is also possible to calculate OPT.

In this case, if the reflectance of the beam splitter 6 is R, then
The output PR of the reflected light 7 is expressed by the following equation (9) using the output P of the laser beam 2, and has a one-to-one correspondence with the output P of the laser beam 2.

pR=R−p (9) Since the sensor 13 outputs an electric signal VF corresponding to the output PR of the reflected light 7, the output P of the laser beam 2 and the electric signal vF from the sensor 13 also have a one-to-one correspondence. , Therefore, the optimum flow rate F calculated by the optimum flow rate calculation device 11 based on the electrical signal VF
OPT corresponds to the output P of the laser beam 2.

FIG. 6 is a diagram showing the processing flow of the optimum flow rate calculation device 11 in this embodiment, and FIG. 7 shows the electrical signal F and the optimum flow rate FOP.
It is a characteristic diagram showing the relationship with T.

〔Effect of the invention〕

As explained above, according to the present invention, the beam splitter is optimally cooled according to the output of the laser beam, so the thermal lens effect of the beam splitter is suppressed and the laser beam output remains stable even when the output changes. As a result, a laser processing device with excellent processing characteristics can be realized.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Figure 3 is a characteristic diagram showing the relationship between the beam diameter of the light transmitted through the beam splitter and the laser output, and Figure 4 is the optimal flow rate of cooling gas to suppress the thermal lens effect. FIG. 5 is a block diagram showing another embodiment of the present invention, FIG. 6 is a flowchart showing the processing procedure of the optimum flow rate calculation device in FIG. 5, and FIG. 7 is a characteristic diagram showing the relationship between A characteristic diagram showing the relationship between the optimal flow rate of cooling gas to suppress the thermal lens effect and the electrical signal output from the sensor. Figure 8 shows the overall configuration of the laser processing device. Figure 9 shows the conventional laser processing device. It is a block diagram which shows an example. 1...Laser oscillator 2...Laser beam 3...Pendar mirror 4...Condensing lens 5...Workpiece
6... Beam splitter 7... Reflected laser beam 8... Transmitted laser beam 9... Nozzle 1
0...Cooling gas supply device 11...Optimum flow rate calculation device 12...Flow rate control device 13...Sensor representative Patent attorney Yoshiaki Inomata (one person) Fig. 1 Fig. 21A No. 3 H Figure 4 Figure 5 Figure 6 Figure 8

Claims (1)

[Claims] In a laser processing device in which a beam light output from a laser oscillator is split into transmitted light and reflected light via a beam splitter, and the transmitted light is used as a processing beam and the reflected light is used as a processing or monitoring beam, the beam splitter is used. A cooling device is provided to inject cooling gas or cooling air to suppress the thermal lens effect of the beam splitter, and the flow rate of the cooling gas or cooling air is controlled to an optimum value according to the output of the laser beam. Laser processing equipment.